Pigment compositions

ABSTRACT

A pigment composition comprising 80-99% weight/weight of copper phthalocyanine containing 1.5-10% weight/weight of peripherally-bound chlorine, and 20-1% weight/weight of a sulphonated copper phthalocyanine derivative having the formula: ##STR1## wherein CuPc represents a copper phthalocyanine residue, R 1 , R 2 , R 3 , R 4 , R 5  and R 6  are the same or different and each represents a hydrogen atom, an alkyl group having from 1 to 22 carbon atoms or a cyclic alkyl group having from 5 to 22 carbon atoms, an aryl,aralkyl,alkaryl or dehydroabietyl group, X represents hydrogen or an alkali metal atom and m, n and p can each be 0 or a value in the range of from 1 to 4, with the proviso that the sum of m, n and p is within the range of from 1 to 4; the composition being characterized by its x-ray diffraction spectrum as resembling the γ--crystal form, and further characterized by the substantial absence of any tendency to crystallize on prolonged contact with aromatic solvents, even at elevated temperatures, which composition, without further pigmentization stages, is suitable for direct incorporation in surface coating media, and provides excellent strength and flow properties therein.

The present invention relates to pigment compositions, and in particularto solvent stable copper phthalocyanine pigment compositions havingx-ray diffraction spectra, resembling the γ-crystal form of copperphthalocyanine, and processes for their preparation.

It is known that copper phthalocyanine may be obtained in five differentcrystal forms, α, β, γ, δ and ε. The particular modification in whichcopper phthalocyanine is produced is of great commercial significancebecause each modification differs greatly from the others in itsproperties, both physical and tinctorial. In relation to tinctorialproperties, α-copper phthalocyanine exhibits red-shade bluepigmentations in surface coating binders, whereas the other commonlyused copper phthalocyanine, the β-modification, exhibits green-shadeblue pigmentations in such substrates. The γ- and δ-modificationsexhibit shades falling between the α and β modifications, and the ε-formis the reddest known form of copper phthalocyanine.

The β-form is the most stable to crystal change in aromatic solvents andis therefore suitable for incorporation into surface coating mediacontaining such solvents. The α-form, although unstable with respect tothe β-form, may be stabilised against conversion to the β-form inaromatic solvents by, for example, incorporating halogen into thephthalocyanine molecule. Thus both the α- and β-forms, when reduced tofinely divided particles, are used commercially as pigments. Incontrast, the γ, δ and ε forms tend to be unstable in aromatic solventsand therefore find little commercial use as pigments.

The various crystal forms may be distinguished from each other and frommixtures of two or more forms by their x-ray diffraction spectra. Thex-ray diffraction spectra of the α- and β-forms of copper phthalocyanineare described in U.S. Pat. No. 2,486,351 and those of the δ- and ε-formsin British Pat. No. 912,526 and German Pat No. 1,181,248, respectively.

In U.S. Pat. No. 2,770,629, there is described the x-ray diffractionspectrum of γ-form copper phthalocyanine and a method for thepreparation of the latter, comprising stirring crude 62-form copperphthalocyanine, at ambient temperature, with 40-60% aqueous sulphuricacid for 3 hours in the presence of xylene sulphonic acid; thereafterpouring the reaction mixture into a bulk of water, stirring with dilutesodium carbonate solution and recovering γ-form copper phthalocyanine byfiltration, washing with water and drying.

Japanese Pat. No. 69,1708, discloses the preparation of γ-form copperphthalocyanine by treatment of copper phthalocyanine with 50-65% aqueoussulphuric acid at an elevated temperature to form copper phthalocyaninemono sulphate and subsequent hydrolysis with a base such as sodiumhydroxide. A method of preparation of phthalocyanine salts capable ofyielding flocculation resistant γ-form phthalocyanine is also describedand claimed in U.S. Pat. No. 2,524,672.

Novel phthalocyanine compounds characterised by their x-ray diffractionspectra, high surface areas, and stability to organic solvents aredescribed and claimed in U.S. Pat. No. 2,910,482. The process for theirpreparation comprises reacting micropulverised anhydrous cupric chloridewith urea, phthalic anhydride, and a monochloro phthalic compound at anelevated temperature in an inert oganic liquid in the presence of areaction catalyst, under vigorous agitation and recovering the productby conventional means.

Disadvantages of this process include the high cost of themonochlorophthalic compound, the necessity to use large amounts of urea,resulting in low throughput and therefore an increase in cost, the needto micropulverize the cupric chloride and the requirement for violentagitation

In contrast to the foregoing, we have found, surprisingly, that copperphthalocyanine in a form resembling the pure or substantially pureγ-crystal form, may be obtained by the addition of specific copperphthalocyanine derivatives to the synthesis of copper phthalocyanine bythe so-called "phthalic anhydride-urea process" in the presence of asmall amount of one or more halogenated phthalic acid derivatives. Theuse of large amounts of halogenated phthalic acid derivatives, and ureaand high shear is thus avoided.

Accordingly, the present invention provides a pigment compositioncomprising 80-99% w/w of copper phthalocyanine containing 1.5-10% w/w ofperipherally bound chlorine, and 20-1%, w/w of a sulphonated copperphthalocyanine derivative having the formula: ##STR2## wherein CuPcrepresents a copper phthalocyanine residue, R₁, R₂, R₃, R₄, R₅ and R₆are the same or different and each represents a hydrogen atom, an alkylgroup having from 1 to 22 carbon atoms or a cyclic alkyl group havingfrom 5 to 22 carbon atoms, an aryl, aralkyl, alkaryl or dehydroabietylgroup, X represents hydrogen or an alkali metal atom and n, m and p caneach be 0 or a value in the range of from 1 to 4, with the proviso thatthe sum of n, m and p is within the range of from 1 to 4; thecomposition being characterised by its x-ray diffraction spectrum asresembling the γ-crystal form, and further characterised by thesubstantial absence of any tendency to crystallise on prolonged contactwith aromatic solvents, even at elevated temperatures.

This pigment composition, without further pigmentization stages, issuitable for direct incorporation in surface coating media, and providesexcellent strength and flow properties therein.

The invention also provides a process for the preparation of saidpigment composition, comprising reacting, in a substituted aromatichydrocarbon solvent boiling above 160° C., at 160°-220° C. for 3-20hours, a mixture of a phthalic compound, a mono-halogenated phthaliccompound, a nitrogen source, an anhydrous copper salt, a reactioncatalyst as conventionally used in phthalocyanine synthesis, and from 1to 20% weight/weight of a sulphonated copper phthalocyanine derivativeof formula I; and recovering the pigment composition by separation fromthe solvent by conventional techniques. As a further aspect, there isprovided the γ-modification of copper phthalocyanine when produced bythis process.

In a further aspect, the present invention also provides a pigmentcomposition comprising the γ-modification of copper phthalocyanine and acompound of formula I, as hereinbefore defined, or a derivative thereof,for example a derivative of the compound of formula I as present in theproduct of the process of the present invention.

In relation to the compounds of formula I, the alkyl, cycloalkyl, aryl,aralkyl or alkaryl substituent groups R₁ -R₆ may be unsubstituted or maybe substituted by hydroxyl, amino, alkylamino, alkoxy or amide groups.

Due to the method preparation of such compounds, namely by reaction ofcopper phthalocyanine with oleum or chlorosulphonic acid, optionallyfollowed by thionyl chloride, and subsequent treatment with an amine ormixture of amines, mixtures of compounds of formula I having varyingdegrees of substitution are produced. Analysis of such mixturestherefore can establish fractional values for m, n and p. Suitablecompounds of formula I are those wherein m has a value in the range 0 to2 and p and n each have a value in the range 0 to 3, subject to theprovisos described hereinbefore.

Copper phthalocyanine pigments which are in the form of pureγ-modification, or which resemble this modification, may bedifferentiated from other known modifications and from mixtures withthese various modifications, not only by shade but especially by meansof x-ray diffraction spectra. The spectrum of the γ-form, shown in theattached FIG. 1, is reproduced from U.S. Pat. No. 2,910,482 wherein theγ-form of chlorine-containing copper phthalocyanine was first described.

Suitable phthalic compounds capable of forming the phthalocyanine ringsystem are, for example, phthalamic acid, phthalimide, phthalic acid,phthalic anhydride and 0-cyano benzoic acid, though phthalic acid oranhydride are preferred. 4-chloro-phthalic acid is the preferredmono-halogenated phthalic compound.

Among copper salts capable of providing the central copper atom of thecopper phthalocyanine molecule, there may be mentioned anhydrous cupricsulphate, anhydrous cupric acetate and anhydrous cuprous chloride butanhydrous cupric chloride is preferred. To ensure a high yield of thedesired copper phthalocyanine, 0.90-1.10 moles of copper salt for every4 moles of the phthalic phthalocyanine ring-forming compound has beenfound satisfactory.

While ammonia and biauret may be mentioned, urea is preferred as asource of nitrogen on account of its low cost and commercialavailability. A satisfactory level of urea is 15-20 moles for every 4moles of the phthalic phthalocyanine ring-forming compound.

Catalysts suitable for the operation of the process are those previouslydescribed in the literature as suitable for phthalocyanine synthesis.Compounds of molybdenum, especially ammonium molybdate or molybdic oxideare preferred as they have been found to give high yields of copperphthalocyanine. A concentration of 0.01-0.03 moles for every 4 moles ofthe phthalocyanine ring-forming compound is generally suitable.

Suitable solvents are those boiling above 150° C. e.g. substitutedaromatic hydrocarbons such as nitrotoluene, but nitrobenzene isparticularly preferred.

Although the quantity of solvent employed in the reaction is notcritical, it is usual to use only sufficient organic solvent to ensure astirrable reaction mass; too much solvent is wasteful and tends toreduce the rate of reaction. A level of 1.5-3 moles per 4 moles ofphthalocyanine ring-forming compound is generally found satisfactory.

A level of 1%-20% w/w of the compound of formula I, based on copperphthalocyanine, has been found satisfactory, though 5-15% w/w ispreferred. Too low a level may give ris to appreciable quantities ofundesirable crystal modifications, whilst too high a level is wastefulof additive and is moreover expensive and reduces the colour strength ofthe product.

The process of the invention may be carried out in any stirred vesselcommonly employed for the preparation of phthalocyanines and capable ofoperation at temperatures from 25° to 220° C. It is found convenient tocharge all reagents cold to the vessel. With stirring, the temperatureis raised cautiously through 100° C., where evolution of volatilematerial takes place, to 170°-180° C. At such a temperature reaction isessentially complete in 6-10 hours, though the yield may be maximised byreacting for up to 18 hours. Alternatively, the reaction may be carriedout at higher temperatures for shorter times. A temperature of 200° C.for 31/2 hours has been found satisfactory, giving high yields of copperphthalocyanine. Although the crystal modifying additive is convenientlyadded at the start of the reaction, it may be added at any time duringthe heating stage at which the temperature of the reaction is less than120° C.

The γ-form copper phthalocyanine product may be separated from thereaction mixture by any of the methods previously known; for example byremoval of the solvent by filtration and drying but preferably by steamdistillation under alkaline conditions followed by hot filtration andwashing with hot water. If desired, further by-products of the reactionmay be removed, by stirring the presscake so obtained in hot aqueousmineral acid, filtering hot, washing with hot water and drying at50°-55° C.

Alternatively the pigment product may be recovered by dilution by anoxygen containing solvent such as methanol, filtering and washing withfurther methanol and drying.

The γ-form copper phthalocyanine pigments obtained according to thepresent invention may, if appropriate, be optimised in theirapplicational properties by conventional techniques. Such techniquesinclude short milling cycles in a ball-mill, solvent treatment e.g. inaccordance with British Pat. No. 1,140,836, or the addition of rosin oran aliphatic amine having from 12 to 22 carbon atoms.

A still further aspect of the present invention concerns a compositioncomprising an organic material and a pigmenting proportion of a pigmentcomposition according to the present invention; and also a method ofpigmenting organic material comprising incorporating therein apigmenting proportion of the pigment composition of the invention.

The proportion of the pigment composition in the organic material isnormally within the range from 0.1% to 20% by weight, based on theweight of the organic material.

Organic materials which may be coloured according to the inventioninclude high molecular weight organic material, e.g. cellulose ethersand cellulose esters such as ethyl cellulose, acetylcellulose andnitrocellulose, polyamides, polyurethanes and polyesters, natural andsynthetic resins such as aminoplasts, especially urea-formaldehyde andmelamine-formaldehyde resins, alkyd resins, phenoplasts, polycarbonates,polyolefins such as polystyrene, polyvinyl chloride, polyethylene,polypropylene, polyacrylonitrile, polyacrylic acid esters, rubber,casein, silicone and silicone resins, individually or in admixture. Itdoes not matter whether these high molecular weight compounds are in theform of plastic masses or melts or solutions or dispersions in the formof spinning solutions.

The pigment compositions of the invention are of particular interesthowever for the colouration of lacquers, paints and printing inks,especially solvent-based decorative and industrial paints and packaginginks.

The pigment compositions of the invention are characterized by shadeintermediate of α- and β-forms, excellent strength, flow and solventstability.

A further advantage of this invention is that, in the products of theprocess of the invention, the compound of formula I or a derivativeformed in the reaction may be retained in the pigment composition,whereby it appears to improve the rheological and colouristic propertiesof the pigment composition in application.

The following Examples further illustrate the present invention.

EXAMPLE 1

82 parts phthalic anhydride, 24 parts 4-chloro phthalic acid, 22.5 partsanhydrous cupric chloride, 175 parts urea, 0.76 parts molybdic oxide,300 parts nitrobenzene and 10 parts of the compound of average formula:##STR3## wherein m=0.5, and n+P=2, were stirred together in a vesselfitted with an air condenser. With stirring, the temperature was raisedto 170° C. over 5 hrs, with a slow heating stage of 21/2 hrs. between95° C. and 110° C. to allow the smooth evolution of volatile material.

The temperature was maintained at 170° C., with stirring, for 16 hrs.after which the reaction mixture was discharged into a second vesselcontaining 35 parts of potassium hydroxide in 235 parts water. Thenitrobenzene was removed by steam distillation and the residue filteredhot, and washed with hot water.

The presscake so obtained was reslurried in a solution of 100 partsconcentrated hydrochloric acid in 500 parts water, stirred for 2 hrs at95° C., then filtered hot, washed acid free with hot water, and dried inan oven at 55° C.

There were obtained 106 parts of a pigment composition having an X-raydiffraction spectrum (FIG. 2) corresponding to that characterising theγ-crystal form, and, typically, a particle size, calculated fromelectron micrographs, of less than 0.1μ.

The crystal modification of the pigment composition, as denoted by itsX-ray spectrum, was unchanged by refluxing the pigment composition for 2hrs in fifty times its own weight of toluene: neither could any evidenceof crystal growth be detected as a result of such treatment.

The pigment composition of this example, without any conditioningtreatment to further reduce its particle size, was incorporated in analkyd-melamine paint medium by ballmilling. When sprayed onto a metalpanel, the paint film was of similar strength but of a redder shade thana similar paint film derived from a β-form copper phthalocyanine,conditioned by salt milling and solvent treatment.

If the synthesis stage of this Example is repeated in the absence of thesulphonated phthalocyanine derivative, a copper phthalocyanine having aparticle size of 20-40μ and an X-ray spectrum similar to that of theβ-modification, is obtained. If both the sulphonated phthalocyaninederivative and the 4-chloro phthalic acid are omitted from thesynthesis, there is obtained a copper phthalocyanine of theβ-modification, having a particle size of 50-60μ.

EXAMPLE 2

82 parts phthalic anhydride, 24 parts 4-chloro phthalic acid, 22.5 partsanhydrous cupric chloride, 175 parts urea, 0.76 parts molybdic oxide,250 parts nitrobenzene and 9.5 parts of the compound of average formula:##STR4## were stirred together. Using the method of Example 1, themixture was reacted and the product recovered and purified to give 96parts of a pigment composition having a X-ray spectrum (FIG. 3)corresponding to that characterising the γ-crystal form.

What we claim is:
 1. A process for the preparation of a pigmentcomposition, which has an X-ray diffraction spectrum resembling theγ-crystal form and does not crystallize on prolonged contact witharomatic solvents, said composition comprising 80-99% by weight ofcopper phthalocyanine containing 1.5-10% by weight of a sulphonatedcopper phthalocyanine derivative having the formula: ##STR5## whereinCuPc represents a copper phthalocyannine residue, R₁, R₂, R₃, R₄, R₅ andR₆ are independently a hydrogen atom, an alkyl group having from 1 to 22carbon atoms or a cyclic alkyl group havig from 5 to 22 carbon atoms, anaryl, aralkyl, alkaryl or dehydroabietyl group, X represents hydrogen oran alkali metal atom and m, n and p can each be 0 or a value in therange of from 1 to 4, with the proviso that the sum of m, n and p iswithin the range of from 1 to 4, said process comprising reacting in asubstituted aromatic hydrocarbon solvent, at a temperature in the rangeof from 160° and 220° C., over a period of 3 to 20 hours, a mixture of aphthalic compound, a mono-chlorinated phthalic compound, a nitrogensource, an anhydrous copper salt, a reaction catalyst and from 1 to 20%weight/weight of a sulphonated copper phthalocyanine derivative offormula I; and recovering the pigment composition by separating it fromthe solvent.
 2. A process as claimed in claim 1 wherein the phthaliccompound is phthalic acid or anhydride.
 3. A process as claimed in claim1 wherein the mono-halogenated phthalic compound is 4-chlorophthalicacid.
 4. A process as claimed in claim 1 wherein the nitrogen source isurea.
 5. A process as claimed in claim 1 wherein the reaction catalystis a compound of molybdenum.
 6. A composition comprising an organicmaterial and a pigmenting proportion of a pigment composition as definedin claim
 1. 7. A composition as claimed in claim 6 wherein the organicmaterial is a lacquer, paint or printing ink.